Howerdel functioned as a guitar technician for Tool during the tour and recording of Ænima, working with Maynard James Keenan, whom he met in 1992. During this time, Howerdel played Keenan some of his songs, and Keenan offered his vocals if Howerdel ever decided to form a band.[2] Despite originally considering a female singer, Howerdel would eventually accept Keenan's offer.[3] In 1999, Howerdel founded A Perfect Circle, and invited Keenan to join.

Howerdel is currently actively involved in his new solo project, Ashes Divide. Howerdel handled nearly all the instruments in the studio for the release, except the drums for which he recruited session musicianJosh Freese. The first single, "The Stone", gained some radio play, and the band toured for the album throughout 2008.[4]

^"Howerdel Exposes Ashes Divide". UltimateGuitar.com. June 5, 2008. Archived from the original on October 6, 2014. Retrieved October 4, 2014. I recently got turned onto this Transcendental Meditation and I would say that it is more along the lines of what I do.